The current three-point seat belt structure is efficient in restricting the movement of a passenger who is deviating toward the front side upon a frontal crash, but has difficulty in maximizing a binding force upon crashes other than the frontal crash.
In a representative example of a new oblique crash test which the National Highway Traffic Safety Administration (NHTSA) will be introducing in 2017, a phenomenon that the shoulder of a dummy escapes from the passenger seat by lateral inertia occurring by the impact of an opposite vehicle colliding in an oblique direction is commonly observed.
When an impact occurs in a left oblique direction of the driver's seat in the new oblique crash test, all occupants of driver's seat and passenger's seat undergo an eccentric inertia in the left (or right) direction. In this case, the driver may receive help from the curtain airbag and the door trim that are located outside the drivers seat, and may not be affected by the shoulder fastening direction of the three-point seat belt.
However, when an occupant of the passenger's seat undergoes the eccentric inertia in the left direction (inner direction of the occupant), the shoulder of the occupant may escape from the seat belt because the direction of the shoulder fastening direction of the passenger is opposite to that of the driver (see FIG. 6A and FIG. 6B).
Due to the shoulder escaping from the seat belt, injury may significantly increase because of the rotation and the lateral behavior of the head/upper body, leading to significant reduction of points upon crash test and serious losses to a company in field accidents besides the crash test.
Accordingly, a new belt restriction structure that can restrict the lateral movement even when the shoulder escapes is needed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.